The present invention is related to an apparatus and method for reducing a hazardous gas content of an effluent from a process chamber.
Fluorocarbon, chlorofluorocarbons, hydrocarbon, and other fluorine containing gases are used in, or formed as a byproduct during, the manufacture of active and passive electronic circuitry in process chambers. These gases are toxic to humans and hazardous to the environment. In addition, they may also strongly absorb infrared radiation and have high global warming potentials. Especially notorious are persistent fluorinated compounds or perfluorocompounds (PFCs) which are long-lived, chemically stable compounds that have lifetimes often exceeding thousands of years. Some examples of PFCs are carbon tetrafluoride (CF4), hexafluoroethane (C2F6), perfluorocyclobutane (C4F8), difluoromethane (CH2F2), perfluorocyclobutene (C4F6), perafluoropropane (C3F8), trifluoromethane (CHF3), sulfur hexafluoride (SF6), nitrogen trifluoride (NF3), carbonyl fluoride (COF2) and the like. For example, CF4 has a lifetime in the environment of about 50,000 years and can contribute to global warming for up to 6.5 million years.
Another hazardous gas is molecular fluorine, F2. Extended exposure to as little as 1 ppm of F2 can be hazardous, and F2 is difficult to breakdown or reduce to non-toxic forms. Previously, effluents containing F2 have been exhausted through exhaust stacks that are sufficiently tall that the concentration of F2 in the air that descends to the ground is below regulatory levels. However, this technique is less than ideal from an environmental standpoint, and also undesirable from a manufacturing standpoint in that the volume of fluorinated gas processes that generate F2 is limited by the height of the exhaust stack. Thus, it is desirable to have an apparatus or method that can reduce the hazardous gas content of effluents, especially effluents containing F2, that may be released from process chambers.
One conventional F2 abatement system uses a hydrogen burn box to reduce F2. However, this system has several disadvantages. For example, a high temperature (generally above 850xc2x0 C.) is necessary for the conversion of F2 to HF in the presence of H2. The heated HF is highly corrosive and hazardous, making its handling costly and dangerous. Additionally, the use of H2 supply lines in a fabrication plant raises fire concerns that further add to the costs and danger of the system.
F2 containing effluents are generated in numerous substrate fabrication processes, as well as in other processes. For example, process gases containing F2, or that form F2 as a byproduct of the process, are used in the etching of layers on substrates, such as oxide, metal and dielectric layers; during chemical vapor deposition processes; and to clean etchant or deposition residue in process chambers. These hazardous compounds may be exhausted from the chamber in the effluent gas stream.
It is desirable to minimize the introduction of such harmful gases and byproducts into the environment. There is also a need to minimize the harmful content of the effluent gas released into the atmosphere in an efficient and inexpensive manner. There is a further need to reduce F2 emissions to the lowest possible levels especially for industries which widely use F2 or F2 producing gases, even though such use is a relatively small component of the overall consumption or release of F2 in the world.
The present invention is useful for reducing a content of hazardous gases, such as F2, in an effluent gas that results from processing of substrates. By hazardous gas it is meant any toxic, harmful or undesirable gas, including but not limited to F2, PFCs, chlorofluorocarbons (CFCs), hydrocarbons, other fluorine containing gases, and other undesirable gases.
In one aspect of the invention, a method of forming and treating an effluent gas from a process chamber comprises introducing a process gas into the process chamber before, during, or after processing a substrate in the process chamber, and forming an effluent gas comprising F2 gas, and passing the effluent gas over a catalyst and thereby reducing the content of the F2 gas in the effluent gas.
In another aspect of the invention, a method of forming and treating an effluent gas from a process chamber comprises introducing a process gas into the process chamber before, during, or after processing a substrate in the process chamber, and forming an effluent gas comprising F2 gas, and introducing an additive into the effluent gas the additive comprising hydrogen species and oxygen species and thereby reducing the content of the F2 gas in the effluent.
In another aspect of the invention, a method of forming and treating an effluent gas from a process chamber comprising introducing a process gas into the process chamber before, during, or after processing a substrate in the process chamber and forming an effluent gas comprising F2 gas, heating the effluent gas and passing the effluent gas over a catalyst, thereby reducing the content of the F2 gas in the effluent.
In another aspect of the invention, a method of cleaning a process chamber comprises introducing a cleaning gas into the process chamber and forming an effluent gas containing F2 and passing the effluent gas over a catalyst, thereby reducing the content of the F2 gas in the effluent.
In another aspect of the invention, a substrate processing apparatus comprises a source of process gas, a process chamber capable of performing a process with the process gas and forming an effluent gas containing F2 and a catalytic reactor adapted to treat the effluent gas to reduce the F2 content thereof.
In another aspect of the invention, a substrate processing apparatus comprises a process chamber capable of performing a process with process gas and forming an effluent containing F2 and an additive source capable of introducing an additive into the effluent gas to reduce the F2 content of the effluent, the additive comprising hydrogen species and oxygen species.